This invention relates, in general, to writing timing information on storage media and, in particular, to determining off-track time shift estimates used in the writing of the timing information.
There is a continuing desire to increase the amount of information that can be stored on various forms of storage media, including floppy and hard disks. One way of increasing the capacity of the storage media is by providing higher track densities. Higher track densities have been made possible by the advent of voice-coil and other types of servo positioners, as well as by the ability to read and write narrower tracks by using, for example, magnetoresistive (MR) head technology.
As technology advances to provide the increased track densities and smaller disk drives, there is an ever-increasing need for more accurately positioned timing information. It is this timing information that is used when writing product servo-patterns on the storage media.
In one example, timing information is provided by writing trigger patterns at various locations of the storage medium. However, in the past, as the trigger patterns were written, one or more systematic errors occurred, which affected the precise positioning of subsequent trigger patterns. In order to reduce the affects of those systematic errors, it is important to determine values for those errors, so they may be taken into consideration when writing trigger patterns.
Based on the foregoing, a need exists for a capability that provides techniques for determining a systematic error. In particular, a need exists for a capability to determine a specific type of systematic error, referred to as an off-track time shift.
The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a method of determining off-track time shift estimates. In one instance, the method includes measuring, at one radial position, a first time interval between a selected criterion and a trigger pattern written on a storage medium; measuring, at another radial position, a second time interval between the selected criterion and the trigger pattern; and determining an off-track time shift estimate using the first time interval and the second time interval.
In one example, the off-track time shift estimate is used to write subsequent trigger patterns on the storage medium.
Further, in one example, the selected criterion includes a plurality of trigger patterns written on the storage medium. The plurality of trigger patterns have a predefined relationship with one another.
As another example, the selected criterion includes a motor index of a storage device. The storage device includes the storage medium.
In yet another example, the selected criterion is another trigger pattern written on the storage medium at a desired radial position. The another trigger pattern and the trigger pattern are, in one instance, written at the same radial position. However, in another instance, they are written at different radial positions.
In another aspect of the present invention, a method of determining off-track time shift estimates is provided. The method includes, for instance, measuring, at a radial position, a first time interval between a first trigger pattern written on a storage medium and a second trigger pattern written on the storage medium; measuring, at the radial position, a second time interval between the second trigger pattern and a third trigger pattern written on the storage medium; and determining an off-track time shift estimate using the first time interval and the second time interval.
In a further aspect of the present invention, an apparatus for determining off-track time shift estimates is provided. The apparatus includes, for example, a measuring unit adapted to measure, at one radial position, a first time interval between a selected criterion and a trigger pattern written on a storage medium. The measuring unit is further adapted to measure, at another radial position, a second time interval between the selected criterion and the trigger pattern. Further, the apparatus includes a computing unit adapted to determine an off-track time shift estimate using the first time interval and the second time interval.
In another aspect of the present invention, an apparatus for determining off-track time shift estimates is provided. The apparatus includes, for instance, a measuring unit adapted to measure, at a radial position, a first time interval between a first trigger pattern written on a storage medium and a second trigger pattern written on the storage medium. Further, the measuring unit is adapted to measure, at the radial position, a second time interval between the second trigger pattern and a third trigger pattern written on the storage medium. The apparatus further includes a computing unit adapted to determine an off-track time shift estimate using the first time interval and the second time interval.
In yet a further aspect of the present invention, an apparatus for determining off-track time shift estimates is provided. The apparatus includes, for example, means for measuring, at one radial position, a first time interval between a selected criterion and a trigger pattern written on a storage medium; means for measuring, at another radial position, a second time interval between the selected criterion and the trigger pattern; and means for determining an off-track time shift estimate using the first time interval and the second time interval.
In another embodiment, an apparatus for determining an off-track time shift estimate is provided. The apparatus includes, for example, means for measuring, at a radial position, a first time interval between a first trigger pattern written on a storage medium and a second trigger pattern written on the storage medium; means for measuring, at the radial position, a second time interval between the second trigger pattern and a third trigger pattern written on the storage medium; and means for determining an off-track time shift estimate using the first time interval and the second time interval.
In yet another aspect of the invention, an article of manufacture is provided. The article of manufacture includes at least one computer usable medium having computer readable program code means embodied therein for causing the determining of off-track time shift estimates. The computer readable program code means in the article of manufacture includes, for example, computer readable program code means for causing a computer to measure, at one radial position, a first time interval between a selected criterion and a trigger pattern written on a storage medium; computer readable program code means for causing a computer to measure, at another radial position, a second time interval between the selected criterion and the trigger pattern; and computer readable program code means for causing a computer to determine an off-track time shift estimate using the first time interval and the second time interval.
In yet another aspect of the present invention, an article of manufacture is provided. The article of manufacture includes at least one computer usable medium having computer readable program code means embodied therein for causing the determining of off-track time shift estimates. The computer readable program code means in the article of manufacture includes, for instance, computer readable program code means for causing a computer to measure, at a radial position, a first time interval between a first trigger pattern written on a storage medium and a second trigger pattern written on the storage medium; computer readable program code means for causing a computer to measure, at the radial position, a second time interval between the second trigger pattern and a third trigger pattern written on the storage medium; and computer readable program code means for causing a computer to determine an off-track time shift estimate using the first time interval and the second time interval.
The present invention advantageously reduces pattern slew when writing trigger patterns on a storage medium. Further, the use of the present invention enables different track pitches to be used when writing the trigger patterns. This advantageously increases the speed at which trigger patterns can be written. As one example, an off-track time estimate can be determined within 3,500 of 18,000 track steps. Once the estimate is determined, the stepping rate can be doubled for the creation of the necessary servo-patterns of the storage medium.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.